This guide demonstrates how to implement Google Login in a Rails application using OmniAuth, without relying on the Devise gem. We’ll utilize OmniAuth for authentication and connect it to a basic Rails authentication system.

Create Basic Authentication

Generate Authentication

in Rails 8, it comes with an authentication generator that we can use. It creates User and Session models and the controllers and views necessary to login to our application. you can find more in the Official Guides

bin/rails generate authentication

Remove Password

because I only want to enable Google Login and remove other login method. so, there is no need to keep the users.password_digest column in database, and delete related file.

let’s remove t.string :password_digest, null: false from [timestamp]_create_users.rb and update the User model to remove the has_secure_password line, as it’s no longer needed.

Run migration

Then migrate the database to add the User and Session tables.

bin/rails db:migrate

Add OmniAuth Gems

Add the required gems to your Gemfile, then run bundle install to install the gems.

# OmniAuth and Google OAuth  
gem "omniauth", "~> 2.1"  
gem "omniauth-google-oauth2", "~> 1.2"  
gem "omniauth-rails_csrf_protection", "~> 1.0"

Configure OmniAuth

Create an initializer for OmniAuth:

touch config/initializers/omniauth.rb

then add the following configuration.

Rails.application.config.middleware.use OmniAuth::Builder do  
  provider :google_oauth2, ENV["GOOGLE_CLIENT_ID"], ENV["GOOGLE_CLIENT_SECRET"]  
end

Ensure that you have the GOOGLE_CLIENT_ID and GOOGLE_CLIENT_SECRET environment variables set in your deployment configuration. read the Official Google Oauth Document to learn how to get GOOGLE_CLIENT_ID and GOOGLE_CLIENT_SECRET value.

Create SocialAccount Model

although in this post, we only need to implement Google Login, but maybe later we may need to add other login method, such as Github Login, so it’s better to save social account info into other model. in this case, it’s called SocialAccount.

rails generate model SocialAccount user:references provider:string uid:string auth_data:json

next, we update generated model as follows:

class SocialAccount < ApplicationRecord  
  belongs_to :user  

  validates :provider, presence: true  
  validates :uid, presence: true, uniqueness: { scope: :provider }  

  def self.from_omniauth(auth)  
    social_account = find_or_initialize_by(provider: auth.provider, uid: auth.uid)  

    unless social_account.persisted?  
      user = User.find_or_create_by!(email_address: auth.info.email) do |u|  
        u.name = auth.info.name  
        u.avatar_url = auth.info.image  
      end  

      social_account.user = user  
      social_account.save!  
    end  

    social_account  
  end  
end

we add function self.from_omniauth to create or find User by email.

Update routes and SessionsController

next we need to add oauth routes to config/routes.rb file.

get "/auth/:provider/callback", to: "sessions#create"  
get "/auth/failure", to: "sessions#failure"

then, upate SessionsController

class SessionsController < ApplicationController  
  def create  
    auth = request.env["omniauth.auth"]  
    social_account = SocialAccount.from_omniauth(auth)  

    start_new_session_for social_account.user  
    redirect_to after_authentication_url  
  end  

  def failure  
    redirect_to root_path, alert: "Authentication failed, please try again."  
  end  
end

Add a button for Google Login in your sessions/new.html.erb:

<%= button_to "Sign in with Google",  
    "/auth/google_oauth2",  
    method: :post,  
    class: "btn btn--primary btn--block",  
    data: { turbo: false } %>

now we successfully add Google Login to our Rails application.

Conclusion

This setup allows you to implement Google Login in your Rails application without using Devise. With OmniAuth, you can extend the application to support other providers like Facebook or GitHub.

Implementing Google Login in Ruby on Rails without Devise